Building Cooling Requirements under Climate Change Scenarios: Impact, Mitigation Strategies, and Future Directions

Abstract

Climate change affects building cooling demand; however, little has been done to explore this effect and show its variability in different climatic zones. This review organizes and summarizes studies which have simulated the impact of climate change on building cooling requirements, and critically analyzes the effectiveness of the mitigation strategies proposed by these studies to alleviate this impact. The review methodology selected studies that reported cooling demand and discussed mitigation strategies in future climates. The studies were then grouped based on their climate zone and impact period. Analysis showed that climate change will increase building cooling demand in all climatic zones, with the greatest increase occurring in temperate and cold climatic zones. By the middle of the 21st century (2040–2080), the average increase in building cooling demand is expected to reach 33%, 89%, 288% and 376%, in tropical, arid, cold, and temperate climates, respectively. These numbers are expected to increase during the end of the 21st century (2080–2100) to 55%, 302%, 734%, and 1020%, for tropical, arid, cold, and temperate climates, respectively. Some mitigation strategies (e.g., thermal insulation, solar shading) showed a potential to reduce the increase in building cooling demand; however, the reduction varied depending on the strategy and climatic zone. Further research is required to determine if existing cooling systems can handle the future increase in cooling requirements.

1. Introduction

Climate change is one of the biggest challenges facing humanity today. Globally, climate change has caused significant consequences on natural and human systems. Due to climate change, glaciers and ice sheets on the planet are melting, causing the global sea level to increase. According to the Intergovernmental Panel on Climate Change (IPCC), the global mean sea level rose by 0.20 m between 1901 and 2018 [1]. The rise in sea level is a significant hazard to coastal life [2,3]. It causes severe damage, such as intense floods and storms that pose a serious threat to humanity worldwide. Climate change also affects global food and water security [4,5,6]. The IPCC (2021) stated that the global surface air temperature increased by 1.09 °C during 2011–2020, compared with the 1850–1900 average. The increase in global surface temperature, combined with the increase in food demand, could reduce global food availability [1]. Moreover, heat stress, extreme precipitation, landslides, air pollution, drought, and water shortages are among the implications of climate change on people, assets, economies, and ecosystems [1]. Due to climate change, droughts are expected to become more frequent, intense, and long-lasting, impacting many sectors of the global economy, notably those requiring food, water, and energy [7].

Climate change can negatively affect the built environment, and of those sectors, buildings are significantly affected by climate change [8,9]. The consequences of climate change on buildings include several vital issues, such as increased flooding and winter storms, increased summer cooling requirements, thermal discomfort, subsidence risk in subsidence-prone locations, and water shortages [10]. Hrabovszky-Horváth et al. (2013) [11] classified such implications into four groups. The first group is the structural impact caused by environmental events, e.g., storms, floods, snow load, and landslides. The second group is building construction, which contains issues related to water supply and construction fixation systems. The third group refers to building material concerns, such as decreased frost resistance, ultraviolet (UV) resistance, and insulation effectiveness. The last group illustrates the impact of climate change on the indoor built environment due to increased outdoor temperatures.

The IPCC describes future climatic projections through five Shared Socioeconomic Pathways (SSPs) that encompass the whole range of potential future increases in anthropogenic climate change drivers [1]. SSP1-1.9 and SSP1-2.6 are two scenarios with very low, and low, greenhouse gas emissions (GHS) emissions, SSP2-4.5 represents the intermediate GHG emissions scenario, whereas SSP3-7.0 and SSP5-8.5 are high, and very high, GHG scenarios, respectively. According to the IPCC’s Sixth Assessment Report (AR6), future climatic projections show that by 2081–2100, the increase in the average global surface air temperature will reach 1 °C to 1.8 °C under SSP1-1.9, and 2.1 °C to 3.5 °C under SSP2-4.5. On the other hand, global temperature increases could reach 3.3 °C to 5.7 °C under SSP5-8.5 [1]. Temperature rise will cause an increase in the cooling energy consumption of buildings [9,12,13]. This increase will have significant consequences for building cooling supply systems. For example, a hotter climate requires higher energy intensity for cooling, compared with a cooler climate [14,15]. Therefore, cooling systems in buildings will need to be modified to match peak cooling load needs throughout the season or year.

The climate change impact on building cooling systems varies from one climatic zone to another [15,16]. There are five main climatic zones globally [17], classified into tropical (category A), arid (category B), temperate (category C), cold (category D), and polar (category E) climate zones. Tropical climates are distinguished by consistently high temperatures and typically high annual precipitation. In the tropical climate zone, the average temperature of all months of the year is 18 °C or above [17]. Arid climate is defined by annual rainfall less than a threshold value that estimates potential evaporation. Temperate climate is found in areas that have an average temperature where the warmest month is above 10 °C, but the average temperature of the coldest month is between 0 °C and 18 °C. Cold climates are where the hottest months have average temperatures below 10 °C, and coldest months below 0 °C. Polar climates are recognized by very low temperatures where the average temperature in the hottest month is below 10 °C [17].

2. Objective and Methods

This review shows how climate change impact on building cooling requirements differs under various climatic zones. Addressing this question can significantly enhance the literature and improve our understanding of the link between future cooling requirements and climate zones. Additionally, this review discusses potential solutions and mitigation strategies to alleviate climate change impact on cooling requirements. The methodology used in this review consists of four phases, as shown in Figure 1.

In the first phase, we surveyed the literature using a combination of three research keyword phrases (climate change, building cooling, mitigation strategies). The survey was conducted using three main databases: Science Direct, Springer, and Wiley Online Library. In this phase, a total of 45 studies covering 75 cities, worldwide, were found, discussing and quantifying climate change impact on building cooling requirements and mitigation strategies. The second phase classified the collected studies into three main categories depending on the content of the study: (i) impact, (ii) mitigation, and (iii) both impact and mitigation.

Phase 3 was the extraction of information from each study. This included the study location (climate zone), baseline year for climate data, expected growth in cooling demand, projection year and emission scenario, and proposed mitigation strategies to lessen the impact of climate change on future cooling demand in buildings. Lastly, the fourth phase in our methodology compared studies, by grouping them under a different basis. For example, similar baseline periods for future studies were grouped. The projection years were grouped into two intervals, representing the middle of the 21st century (2040–2080) and the end of the 21st century (2080–2100).

Figure 2 shows the distribution of the studied cities across the climate zones. Most of the reviewed studies were located in the temperate climate zone. This review is organized as follows: Section 1 introduces future climate projections and climate change implications on building cooling requirements. Section 2 describes the research objectives and methodology. Section 3 shows the differences in climate change implications on building cooling requirements under different climatic zones. Section 4 describes the potential solutions and mitigation strategies, that these studies suggested, to adapt to the impact of climate change on building cooling requirements. Section 5 discusses and analyzes the main results. Section 6 concludes the main findings and provides suggestions to advance this field.

3. Climate Change Impact on Building Cooling Requirements

This section presents how previous literature has discussed the effect of climate change on building cooling demand. The section starts with studies conducted on a large scale, to pave the road for small-scale studies that are categorized under four climatic zones: tropical (category A), arid (category B), temperate (category C), and cold (category D). The review excluded the fifth climatic zone, polar (category E), since no studies investigated the cooling requirements in the found literature.

3.1. Large Scale Studies

Several global studies have been conducted to examine the cooling energy requirements of buildings under climate change impact. Gi et al. (2018) evaluated thermal demand and energy consumption in residential buildings globally, under different climate change scenarios. They confirmed that cooling requirements by 2050 could be 3.8 to 4.5 times higher than in 2010 [18]. Another study [19] developed an energy model to evaluate the energy demand in buildings across the 21st century, considering various SSPs. The results showed that in developing regions, the total increase in building energy demand was being heavily driven by cooling energy usage. The global need for cooling in buildings under all scenarios increased from 14% in 2010, to 36–71% in 2100 [19]. A recent study stated that, by 2050, global cooling energy consumption would be double under the SSP3, and triple under the SSP1 [20]. The study also emphasized that the need for building cooling is expected to be higher in developing regions with hot and warm climates [20]. Santamouris (2016) predicted that the average demand for cooling in 2050 will increase to 750% for residential buildings and 275% for commercial buildings [21].

3.2. Climate Zone-A “Tropical”

Three studies conducted in the United States investigated climate change impacts on building future cooling demand [14,22,23]. Wang and Chen (2014) [14] and Shen (2017) [23] used a global climate model (GCM) to create future weather data to assess the impact of climate change on energy use for building cooling in Miami, Florida, under A2 emission scenarios. It was concluded that building cooling energy requirements could increase by 26.60% in 2040–2069 [23], and 50% by 2080 [14]. Comparable results were obtained by Jiang et al. (2018) in Key West, Florida. Jiang et al. (2018) found that cooling demand for apartment buildings is expected to increase by 28% by 2050, and 48% by 2080, under the A2 emission scenario [22]. Yau and Hasbi (2017) used TRNSYS software to simulate future cooling demand in Kuala Lumpur, Malaysia. They found that building cooling demand would increase by 8.08% by 2050 and 11.70% by 2080 [24].

Kameni Nematchoua et al. (2015) discussed the future demand for cooling in buildings in Douala, Cameroon. They looked at daily data from five Cameroon weather stations for the previous 40 years. They used a GCM model and the A2 emission scenario to create future climate data. It was observed that cooling energy consumption increased by 19.7% between 2013 and 2043, and almost by 50% between 2045 and 2075 [25]. The future cooling requirement in Bengaluru, India, was investigated using projections of cooling degree days (CDD) under two climate scenarios [26]. The investigation showed that CDD would increase by between 50% and 60% by 2080 under representative concentration pathway (RCP) 4.5, and around 80% under RCP8.5 [26]. A study [27] conducted in Belém, Brazil, reported that under the A2 emission scenario, cooling requirements would increase by 70% by 2050, and by 111% by 2080. In Ghana, the increase in cooling need for buildings was expected to be 50% in the Greater Accra region and 15% in the Ashanti region by 2050 under the A1B emission scenario [28].

3.3. Climate Zone-B “Arid”

In Iran, a study [29] attempted to quantify the impact of climate change on building energy demand based on the A2 climate scenario. The study focused on three cities located on the southern coast of Iran: Bushehr, Bandar Abbas, and Chabahar. The results revealed that the cooling energy (kWh/m²) requirement increased from 8609 to 9842, 10,027 to 11,454, and 10,392 to 11,771, in Bushehr, Bandar Abbas, and Chabahar, respectively [29]. In other words, the energy required for building cooling increased by 13–14% by the end of 2060, compared with previous data collected from 1961 to 1990. Moreover, by 2060, cooling demand is expected to be responsible for more than 95% of total building energy demand in Bandar Abbas and Chabahar, and more than 80% in Bushehr [29]. Andric and Al-Ghamdi (2020) emphasized that the gap between outside and indoor temperatures may rise in Qatar due to climate change. As a result, the cooling energy requirement will increase, driving total building energy consumption to increase by 30% by 2080 [30].

CDD future trends were investigated in Ahmedabad, in western India [26], which showed that by 2080 the CDD would increase to about 20% and 40%, under scenarios RCP4.5 and RCP8.5, respectively. Heracleous et al. (2021) evaluated the cooling degree hours (CDH) for a secondary school in Nicosia, Cyprus, in 2050 and 2090. They found that under the A1B emission scenario, the CDH increased by 50% to 80% by 2050, and by 135% to 213% by 2090 [31]. Shen (2017) quantified the future cooling demand for buildings in Phoenix, Arizona, United States [23]. The results showed that cooling demand could increase by 17.40% during 2040–2069. In Spain, cooling demand would significantly increase by 129% and 349%, in Granada and Salamanca, respectively, by 2050, and by 239% and 645%, by 2080 [32].

3.4. Climate Zone-C “Temperate”

A study in the United States quantified the cooling energy required for apartment buildings under future climate conditions considering the A2 emission scenario [22]. The study investigated building cooling demands in different cities in Florida, and showed that by 2050, the increase in building cooling demand would reach 36% in Daytona Beach, 40% in Jacksonville, 35% in Orlando, 42% in Pensacola, 45% in Tallahassee, and 34% in Tampa [22]. In 2080, cooling demand in the these cities will increase by 62%, 71%, 61%, 74%, 80%, and 59%, respectively [22]. Chakraborty et al. (2021) developed an artificial intelligence model to study the effects of climate change on building cooling consumption in San Antonio and New York, United States [33]. The results revealed that cooling demand will increase by 24.5%, 33.3%, 57.8%, and 87.2% in San Antonio and by 37.1%, 47.5%, 85.3%, and 121% in New York, under SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5, respectively. During 2001–2100, the average demand for cooling in China could increase by 24.2% in Kunming, 11.4% in Shanghai, and 14.1% in Hong Kong, under the B1 emission scenario [15]. Liu, Kwok, Lau and Tong et al. (2020) found that in Hong Kong, building cooling energy could increase by 29.79% and 36.71% by 2050, and by 27.27% and 54.25% by 2090, under RCP4.5 and RCP8.5, respectively [34].

An assessment of the climate change implication using dynamic simulation was performed to analyze building energy performance in Milan in the short term (2021–2040) and the long term (2081–2099) [35]. Three building types (single-family, multi-family, and apartment blocks) were examined under two climate scenarios (RCP4.5 and RCP8.5). The study showed that in 2021–2040, the cooling demand in apartment blocks could rise by 47.10% and 56.40% under RCP4.5 and RCP8.5, respectively. However, in the long term (2081–2099), it was concluded that the increase in cooling demand could be 73.7% under RCP4.5 and 174.3% under RCP8.5 [35]. The impact of climate change on building cooling energy in four Italian cities was quantified by a simulation study considering the A2 emission scenario [32]. The result showed that in 2050, the energy required for cooling in buildings would increase by 261% in Milan, 71% in Palermo, 172% in Pescara, and 144% in Rome. A further increase is expected in 2080, namely, 468% in Milan, 142% in Palermo, 313% in Pescara, and 272% in Rome [32]. Another study reported that Benevento city, Italy, is heading toward a dominant cooling climate as the increase in CDD is expected to vary from +15% (RCP4.5) to + 104% by 2080, under RCP8.5 [36].

The effect of global warming on cooling requirements was investigated in Delhi, India [26]. It was found that, due to rising temperatures, the number of CDD would increase by 24.30% under RCP4.5, and 52.70% under RCP8.5. Consequently, cooling requirements for buildings will increase by a similar amount by the end of 2080 [26]. Berger et al. (2014) investigated the cooling requirement for buildings in Vienna, Austria, under future climate conditions [37]. Findings demonstrated that the cooling demand would grow by 28% to 92% by 2050 under the A1B emission scenario. In the near term (2026–2045), the increase in peak cooling load in buildings in Geneva, Switzerland, could reach 28.5% [38]. However, two other studies in Switzerland reported a higher increase in cooling demand. Buildings in Switzerland are expected to have a significant increase of 223% to 1050% in cooling requirements for the period 2050–2100 [39]. In 2050, the Swiss service sector could have an approximate increase in cooling requirements by 400%, 500%, and 600%, under RCP2.6, RCP4.5, and RCP8.5, respectively [40].

Bamdad et al. (2021) estimated the future energy demands under climate change for a typical building in two cities in Australia, namely, Canberra, the capital of the Commonwealth of Australia, and Brisbane, the capital of the state of Queensland [41]. The result showed that by 2080, cooling demand could increase by 19.6% in Canberra and by 19% to 23.9% in Brisbane, under the A2 emission scenario. A thermal analysis conducted in Japan by Shibuya and Croxford (2016) expected the cooling load to increase by 32.80% in Tokyo and 19.80% in Naha, by 2090, under the A2 emission scenario [42]. A simulation study conducted in Taipei, Taiwan, aimed to evaluate cooling demand in buildings under future climate conditions [43]. The result of the study indicated that under the A1B emission scenario, the increase in cooling demand in buildings would reach 59% and 82%, by 2050 and 2080, respectively [43]. In two Brazilian cities, namely, Curitiba and Florianopolis, future building cooling demand was estimated under the A2 emission scenario [27]. The obtained result indicated that the cooling demand of Curitiba buildings could increase by 210% and 400%, in 2050 and 2080, respectively, while in Florianopolis, these percentages were 120% and 197%, in 2050 and 2080, respectively.

In Greece, cooling energy use in buildings could rise by 248% by 2100 [44]. Cooling requirements for buildings in London could almost double by 2030 due to climate change [45]. Ciancio et al. (2020) modeled a hypothetical residential building to simulate climate change impact on cooling needs in different cities across Europe [32]. The result stated, that by 2050, cooling need is expected to rise by 1371% in London, 427% in Paris, and 937% in Porto, under the A2 emission scenario. In Växjö, Sweden, building cooling demand is expected to increase by 39% by 2050 under RCP4.5 [46].

3.5. Climate Zone-D “Cold”

Implications of climate change on building cooling demand were studied in Jinan, eastern China [47]. The findings revealed that residential building cooling energy is vulnerable to climate change, with total annual cooling energy increasing by 30.7% and 80.3%, by 2050 and 2080, respectively, relative to 2020. Another study in China found that building cooling energy use could increase by 18.5% in Harbin and 20.4% in Beijing across the 21st century [15]. Berardi and Jafarpur (2020) used statistical and dynamical approaches to generate weather data to simulate building energy demand under the A2 emission scenario in Canada, namely, for Toronto in Ontario [48]. They found that by 2070, the average increase in cooling energy usage intensity will vary from 15% to 126%, depending on the type of building.

Another study conducted in Canada adopted the RCP8.5 scenario to evaluate future building cooling demand in Quebec and Toronto [49]. The findings showed that in 2056–2075, growth in building cooling demand will reach 34.6% in Quebec and 32.2% in Toronto. Wang and Chen (2014) discussed the effect of climate change on building cooling requirements in Chicago and Minneapolis [14]. The result stated that cooling demand differs among building types. They also expected that by 2080, cooling energy demand for apartment buildings could increase by approximately 80% and 100%, in Chicago and Minneapolis, respectively. A study conducted in Chicago found that building cooling demand could increase by 24.8% to 32.9%, from 2040 to 2069, under the A2 emission scenario [23]. Under the RCP8.5 scenario, cooling demand for residential buildings in Kaunas, Lithuania, was estimated to increase by 1.8% to 2.1% by 2080, compared with 2020 [50].

Shibuya and Croxford (2016) evaluated the expected increase in the building cooling load in Sapporo, Japan [42]. They adopted the A2 emission scenario to produce future weather data. It was found that due to climate change, the cooling load in buildings could increase by 46.7% by 2090. Jylhä et al. (2015) expected cooling demand for buildings in Vantaa, Finland, to increase by 29% by 2050, and 82% by 2100, under the A2 emission scenario [51]. Ciancio et al. (2020) simulated the energy demand for buildings in different European cities considering the A2 emission scenario [32]. Building cooling demand in Cluj-Napoca, Romania, would increase by 472% by 2050, and 871% by 2080 [32]. A higher demand in building cooling was found in Copenhagen, Denmark, with an increase of 928% in 2050 and 2297% in 2080 [32]. Building cooling demand in Prague, Czech Republic, is expected to increase by 974% and 2318% in 2050 and 2080, respectively [32]. A significant increase in building cooling is expected to occur in Göteborg, Sweden, with an increase of 9945% by 2050 and by 30,945% by 2080 [32].

4. Potential Solutions and Mitigation Strategies

This section describes how previous literature studies investigated the impact of using different strategies and potential solutions to mitigate the effect of climate change on building cooling requirements across different climate zones.

Different mitigation techniques and measures were found in the literature, which were grouped into ten strategies. However, out of the ten strategies, only seven (shown in Figure 3) were discussed under future climate conditions, while the other strategies were only discussed in the present climate. Installation of efficient windows could reduce heat transfer between inside and outside environments. Different techniques were grouped under this category, such as double or triple pane windows, visible transmittance (VT) and solar transmittance (ST) of glazing material, and the thermal conductivity of the window. For example, reducing the value of VT and ST of glazing material reduces the amount of light passing through the window, leading to a cooler indoor environment [52]. Window-to-wall ratio (WWR) is another category related to building windows; however, this technique requires changing the area of the window with respect to the wall area at the design stage of the building and does not include changing the type of window or the glazing material. New technologies, including electrochromic glazing (an electronically tintable window that can be controlled to improve indoor comfort and reduce solar radiation), are expected to become available in the market and could be used as mitigation strategies in the future years [53]. The solar shading category includes techniques such as window shading, overhangs, side fins, and shading devices. These techniques control the amount of solar energy the building directly absorbs from the sun [42].

The thermal insulation category refers to the addition of insulation layers to the envelope elements of the building (floors, walls, and roofs), which enhance the heat transfer coefficient of these elements and, therefore, reduce the heat transfer between the indoor and outdoor environment [54], and as a result, decreases the cooling demand. Polystyrene, polyurethane, and glass wool are the most available and used insulation materials, while other new materials are emerging, such as phase-change materials (PCM), aerogels, and vacuum insulation panels [8]. Thermal mass was considered a separate category as it requires a change in the building structure (pre-construction). Urban morphology is a large-scale mitigation strategy that refers to the compactness and density of buildings and building height to street width, among other factors [9]. Natural ventilation is the process of removing and providing air to the building naturally (wind-driven) without the need for mechanical systems [55]. The functioning of natural ventilation at night to remove surplus heat and lower indoor temperatures is referred to as night ventilation. Other techniques were found in the literature, such as light color building shell, indoor comfort temperature, and efficient lighting.

4.1. Climate Zone-A “Tropical”

The application of phase change materials (PMC) and other passive measures, and their impact on building cooling, were studied in four cities in Madagascar that have equatorial climates [56]. It was found that thermal insulation combined with PCM reduced cooling energy usage by 12%, and increased the comfort rate by 3%. However, a higher cooling energy reduction of 19.4% was achieved by integrating external shading and thermal insulation. A study attempted to examine the ability of passive cooling to reduce building overheating in two cities in Honduras (San Pedro Sula and Tegucigalpa) based on current and future climates, considering the A2 emission scenario [57]. The passive cooling parameters used in this study included natural ventilation, WWR, and wall absorbance. The result stated that by applying the best combination of passive cooling strategies, the risk of building overheating in Tegucigalpa was zero in the present climate and only 0.4% in 2050. The overheating risk in San Pedro Sula, was 20.4% and 37.5% in the present and future climate, respectively.

Jiang and O’Meara (2018) explored the impact of mitigation measures on apartment building cooling in Miami, United States, in present and future climates. They stated that changing the thermal resistance for the walls and roof can reduce the cooling requirement by 3–5%. It was also observed that visible and solar transmittance and the K value of windows could reduce the cooling requirement by 3–3.5%, under the future scenario [52]. Dodoo and Ayarkwa (2019) investigated future cooling demand for buildings in the Greater Accra Region under the A1B emission scenario [28]. The result showed that thermal insulation could reduce cooling demand by 11.9% in the present climate and 7.2% in 2050 [28]. Shading devices and reduced WWR could lower cooling demand by 6.1% and 2.8% in the present climate, and by 3.40% and 1.90% in 2050 [28].

4.2. Climate Zone-B “Arid”

Urban morphology was investigated to show its impact on cooling demand in Tehran, Iran [58]. The findings showed that urban morphology has a remarkable impact on building energy, reducing cooling demand by 10%. It also indicated that cooling demand in urban areas with high density was less than in urban areas with low density [58]. A study presented the influence of different design measures on building cooling in Al-Ain, UAE [59]. The findings revealed that design measures, including thermal insulation and thermal mass are vital in mitigating the impact of global warming on building cooling. It also stated that building cooling demand in 2050 could be reduced by 19.7% by thermal insulation, 12.6% by thermal mass, 3.4% by shading devices, 5.5% by an efficient window system, and 3.90% by reduced WWR. A study in Qatar [60] revealed that improving window quality and lighting efficiency can reduce building cooling demand by 5% and 10%, respectively. Using light color in the exterior shell instead of medium color reduced cooling demand by 12%. Lastly, cooling requirement was reduced by 27% as a result of reducing the external wall U-value [60].

4.3. Climate Zone-C “Temperate”

Mushtaha et al. (2021) attempted to reduce the requirements of building cooling in Palestine, Gaza, using three passive design elements [61]. It was observed that applying natural ventilation increased cooling demand by 24.4% [61]. On the other hand, a reduction in cooling load by 53.5% and 64.3% was achieved by using thermal insulation and shading devices, respectively [61]. Liu et al. (2020) assessed the efficacy of the passive design parameters for Hong Kong residential buildings under future climate scenarios. The study found that solar shading is an effective option to reduce cooling energy, and by the end of this century, the window insulation effectiveness could rise to 329% [62]. A combination of solar protection and thermal insulation techniques can decrease the yearly cooling load in residential buildings by 55.1% and 56.7% under current and future climates, considering RCP8.5 [62]. The cooling requirement for an apartment block in Milan is expected to increase by 174.3% in 2081–2099 under RCP8.5 [35]. Nevertheless, this percentage is expected to reduce to 110.8% by applying thermal insulation to the building envelope components.

A study in Switzerland explored the potential of applying night ventilation and window shading to reduce the cooling demand in buildings under future climate conditions considering RCP4.5 [63]. The result indicated that by 2050, the application of window shading could lower the cooling requirements in Swiss buildings by 71%, and night ventilation could reduce cooling demand by 38%. However, a reduction of 84% could be achieved by combining both strategies, i.e., window shading and night ventilation. In Canberra and Brisbane, Australia, a study [41] evaluated the effect of using three design strategies on the building cooling requirement in present and long term (2080) climates. The result stated that optimizing wall insulation, window type, and overhang depth under present climate conditions could reduce the cooling requirement by 56% in Canberra and by 49% in Brisbane. However, these percentages were expected to reduce to 54% in Canberra and 46.7% in Brisbane in the long-term, considering the A2 emission scenario [41].

Shibuya and Croxford (2016) attempted to mitigate the impact of climate change on building cooling in Japan [42]. They studied the effect of combining five different measures: efficient glazing, thermal insulation, indoor comfort temperature, shading devices, and night cooling. The simulation outcome showed that cooling demand in 2090 could reduce by 57.4% in Tokyo, and by 43.5% in Naha. A study conducted in Taipei, Taiwan, revealed that cooling demand would increase significantly under climate change [43]. However, thermal insulation could reduce cooling demand by 31.30% to 42.3% in 2050, and by 22.8% to 33.2% in 2080. Shading devices would decrease cooling demand by 37.5% in 2050 and 27.7% in 2080 [43].

4.4. Climate Zone-D “Cold”

In this climate zone, most of the found studies discussed the reduction of heating demand. However, studies that discussed mitigation strategies related to cooling requirements were rare. In Toronto, Canada, Berardi and Jafarpur (2020) conducted a simulation study to investigate climate change impact on energy requirements in different building types [48]. It was observed that the cooling requirement in all buildings would increase by 2070. However, climate change had less impact on buildings with lower WWR, higher area to floor ratio, and higher thermal insulation [48]. Another study in Canada in Quebec and Toronto simulated the effect of adding more insulation to the wall and triple glazing, on building energy demand [49]. The study considered the impact of future climate (RCP8.5) on cooling and heating demands. Adding higher wall insulation and triple glazing to office buildings significantly reduced the heating load; however, it increased the cooling load by 19.5% in Quebec and 22.2% in Toronto [49]. In Sapporo, Japan, the building cooling load of buildings was quantified before and after applying different mitigation strategies: efficient glazing, thermal insulation, indoor comfort temperature, shading devices, and night cooling [42]. Combining these measures in the building could reduce the cooling load by 71.97% in 2090.

5. Discussion and Critical Analysis

5.1. Future Building Cooling Demand

Globally, the cooling requirement of buildings will increase due to climate change. Nevertheless, this increase varies from one climatic zone to another. The summary of the expected increase in building cooling demand across climate zones is illustrated in Table 1 and Table 2 under different baseline and projection periods. The projection period for Table 1 is 2040–2080, and 2080–2100 for Table 2.

The increase in building cooling demand in climate zone category (A) varied among the reviewed studies. The lowest increase (8%) was found in Kuala Lumpur, Malaysia, in the projection period 2040–2080 [24]. Conversely, the highest growth in cooling demand was found in the projection period 2080–2100 in Belém, Brazil, by 111% [27]. It was noticed that cooling demand increased with time. For example, comparing the studies in Table 1 and Table 2, it can be observed that the values of building cooling demand in Kuala Lumpur, Miami, and Key, were 8%, 26.6%, and 28%, respectively, in 2040–2080. These values increased to 11.7%, 50%, and 48%, in 2080–2100. In the arid climate zone category (B), all Table 1 studies shared the same baseline period (1961–1990) and emission scenario (A2). Therefore, the values of future cooling demands were expected to be close to each other, which was illustrated by two studies, namely, in Iran [29] and the United States [23]. However, the study conducted in Spain showed significantly higher values in the middle of the 21st century. This difference could be due to the different sub-climate zone as Granada and Salamanca have a cold semi-arid climate (BSk), while the cities studied in Iran and the United States are dominated by a hot arid-desert climate (BWh).

Most of the studied cities are located in the temperate climate zone category (C). Table 1 and Table 2 show that studies in this climate had various emission scenarios, baseline periods, and a wide range of future cooling demand values. It was noticed that the percentages for the increase in building cooling demand in Aberdeen, Belfast, and London were extremely higher than the other cities. These high percentages were due to the absence of cooling systems or low cooling demands reported in the comparable baseline periods. For instance, the cooling demand in Aberdeen is expected to increase from 0 kWh in 1961–1990 to 50 kWh (5000%) in 2050 and 236 kWh (23,600%) in 2080 [32]. Therefore, in such cases, installing cooling systems is necessary to meet future cooling demands. The relation between the applied emission scenario and the increase in cooling demand is clearly expressed in Table 1 and Table 2. As GHS emissions increase, cooling demands of buildings increase. For example, in Table 2, the cooling demands in Hong Kong [34] and Milan [35] increased from 27.27% and 73.70%, respectively, under RCP4.5, to 54.25% and 174.3% under RCP8.5.

Similar to climate zone C, the future increase in cooling demand in climate zone D had a wide range. The highest increase in cooling demand (9945% in 2050 and 30,945% in 2080) was reported in Göteborg. However, Göteborg had low cooling (11 kWh) demand in the baseline period [32]. These percentages will not be considered because of the significant variation observed compared with other studies in the same climate zone. It was also observed that the study conducted by Ciancio et al. (2020) reported significantly higher percentages in the increase in cooling demands than other studies in climate zones B, C, and D [32]. This variation could be due to the methodology or the building type simulated in that study. For example, if we excluded the percentages reported in that study, the range of increase in cooling demand during the middle of the century in all climate zones would reduce as follows: 8% to 70% in climate zone A, 13% to 17.4% in climate zone B, 28% to 210% in climate zone C, and 15% to 126% in climate zone D.

Figure 4 compares the expected increase in cooling demand during the middle of the century (excluding Göteborg and Aberdeen), considering the baseline period of 1961–1990 under the A2 emission scenario. It was observed that climate zones C and D had a higher increase in cooling demand than zones A and B. This high growth was due to the change in the climate, and specifically the increase in outdoor temperature. Cold countries would face a shift in the days with comfortable indoor temperatures, to warm days that require cooling. This justified the high increase in cooling demand in climate zones C and D; however, the consequences in hot countries could be severe on the existing cooling system even if cooling demand increased by a small percentage, since the cooling system in such countries is already overloaded during summer.

Table 1. Expected increase in building cooling demand during the middle of the 21st century (2040–2080).

Study	Climate Zone	Country	City	Emission Scenario	Baseline Year	Projection Year	Cooling Demand Increase
[23]	A	United States	Miami	A2	1961–1990	2040–2069	26.6%
[22]			Key West			2050	28%
[25]		Cameroon	Douala		1970–2000	2013–2043	19.7%
						2045–2075	50%
[24]		Malaysia	Kuala Lumpur	-	2000	2050	8.08%
[28]		Ghana	Greater Accra Region	A1B	2000–2009		50%
			Ashanti Region				15%
[27]		Brazil	Belém	A2	2015		70%
[29]	B	Iran	Bushehr	A2	1961–1990	2060	14.32%
			Bandar Abbas				14.23%
			Chabahar				13.27%
[23]		United States	Phoenix			2040–2069	17.4%
[32]		Spain	Granada			2050	129.35%
			Salamanca				349.26%
[32]	C	UnitedKingdom	Aberdeen	A2	1961–1990	2050	5000%
			London				1370.68%
		France	Bordeaux				227.22%
		Italy	Pescara				172.14%
			Rome				143.53%
			Milan				260.68%
			Palermo				70.7%
		France	Paris				427.35%
		Portugal	Porto				489.98%
[22]		United States	Daytona Beach				36%
			Tallahassee				45%
			Tampa				34%
			Jacksonville		1991–2005		40%
			Orlando				35%
			Pensacola				42%
[34]		China	Hong Kong	RCP4.5	1979–2003	2065	29.79%
				RCP8.5			36.71%
[35]		Italy	Milan	RCP4.5	1982–1999	2021–2040	47.1%
				RCP8.5			56.4%
[37]		Austria	Vienna	A1B	1980–2008	2050	28–92%
[46]		Sweden	Växjö	RCP4.5	1996–2005		39%
[43]		Taiwan	Taipei	A1B	1993–2014		59%
[27]		Brazil	Curitiba	A2	2015		210%
			Florianopolis				120%
[48]	D	Canada	Ontario	A2	1959–1989	2070	15% to 126%
[23]		United States	Chicago		1961–1990	2040–2069	24.8%
[32]		Romania	Cluj-Napoca			2050	472.37%
		Denmark	Copenhagen				928.28%
		Sweden	Göteborg				9945.45%
		Czech Republic	Prague				973.74%
[51]		Finland	Vantaa		1980–2009		29%
[49]		Canada	Quebec	RCP8.5	1998–2014	2056–2075	34.6%
			Toronto				32.2%
[47]		China	Jinan	A2	2020	2050	30.7%

Table 1. Expected increase in building cooling demand during the middle of the 21st century (2040–2080).

Study	Climate Zone	Country	City	Emission Scenario	Baseline Year	Projection Year	Cooling Demand Increase
[23]	A	United States	Miami	A2	1961–1990	2040–2069	26.6%
[22]			Key West			2050	28%
[25]		Cameroon	Douala		1970–2000	2013–2043	19.7%
						2045–2075	50%
[24]		Malaysia	Kuala Lumpur	-	2000	2050	8.08%
[28]		Ghana	Greater Accra Region	A1B	2000–2009		50%
			Ashanti Region				15%
[27]		Brazil	Belém	A2	2015		70%
[29]	B	Iran	Bushehr	A2	1961–1990	2060	14.32%
			Bandar Abbas				14.23%
			Chabahar				13.27%
[23]		United States	Phoenix			2040–2069	17.4%
[32]		Spain	Granada			2050	129.35%
			Salamanca				349.26%
[32]	C	UnitedKingdom	Aberdeen	A2	1961–1990	2050	5000%
			London				1370.68%
		France	Bordeaux				227.22%
		Italy	Pescara				172.14%
			Rome				143.53%
			Milan				260.68%
			Palermo				70.7%
		France	Paris				427.35%
		Portugal	Porto				489.98%
[22]		United States	Daytona Beach				36%
			Tallahassee				45%
			Tampa				34%
			Jacksonville		1991–2005		40%
			Orlando				35%
			Pensacola				42%
[34]		China	Hong Kong	RCP4.5	1979–2003	2065	29.79%
				RCP8.5			36.71%
[35]		Italy	Milan	RCP4.5	1982–1999	2021–2040	47.1%
				RCP8.5			56.4%
[37]		Austria	Vienna	A1B	1980–2008	2050	28–92%
[46]		Sweden	Växjö	RCP4.5	1996–2005		39%
[43]		Taiwan	Taipei	A1B	1993–2014		59%
[27]		Brazil	Curitiba	A2	2015		210%
			Florianopolis				120%
[48]	D	Canada	Ontario	A2	1959–1989	2070	15% to 126%
[23]		United States	Chicago		1961–1990	2040–2069	24.8%
[32]		Romania	Cluj-Napoca			2050	472.37%
		Denmark	Copenhagen				928.28%
		Sweden	Göteborg				9945.45%
		Czech Republic	Prague				973.74%
[51]		Finland	Vantaa		1980–2009		29%
[49]		Canada	Quebec	RCP8.5	1998–2014	2056–2075	34.6%
			Toronto				32.2%
[47]		China	Jinan	A2	2020	2050	30.7%

Table 2. Expected increase in building cooling demand during the end of the 21st century (2080–2100).

Study	Climate Zone	Country	City	Emission Scenario	Baseline Year	Projection Year	Cooling Demand Increase
[14]	A	United States	Miami	A2	1960	2080	50%
[22]		United States	Key West Florida		1961–1990		48%
[24]		Malaysia	Kuala Lumpur	-	2000		11.7%
[27]		Brazil	Belém	A2	2015		111%
[59]	B	UAE	Al-Ain	-	1961–1990	2100	23.5%
[32]		Spain	Granada	A2		2080	239%
			Salamanca				645%
[32]	C	United Kingdom	Aberdeen	A2	1961–1990	2080	23,600%
			Belfast				1100%
			London				3695%
		France	Bordeaux				434%
		Italy	Milan				468%
			Palermo				142%
			Pescara				313%
			Rome				272%
		France	Paris				853%
		Portugal	Porto				937%
[22]		United States	Tallahassee				80%
			Tampa				59%
			Daytona Beach				62%
[39]		Switzerland	Switzerland	-		2050–2100	223% to 1050%
[34]		China	Hong Kong	RCP4.5	1979–2003	2090	27.27%
				RCP8.5			54.25%
[42]		Japan	Tokyo	A2	1981–2000	2090	32.8%
			Naha				19.8%
[35]		Italy	Milan	RCP4.5	1982–1999	2081–2099	73.7%
				RCP8.5			174.3%
[22]		United States	Jacksonville	A2	1991–2005	2080	71%
			Orlando				61%
			Pensacola				74%
[43]		Taiwan	Taipei	A1B	1993–2014	2080	82%
[33]		United States	San Antonio	SSP126	2020	2100	24.5%
				SSP245			33.3%
				SSP370			57.8%
				SSP585			87%
			New York	SSP126			37.1%
				SSP245			47.5%
				SSP370			85.3%
				SSP585			121%
[41]		Australia	Canberra	A2	-	2080	19.6%
			Brisbane		-	2080	19% to 23.9%
[32]	D	Romania	Cluj-Napoca	A2	1961–1990	2080	871%
		Denmark	Copenhagen				2297%
		Sweden	Göteborg				30,945%
		Czech Republic	Prague				2318%
[14]		United States	Chicago		1960		80%
			Minneapolis				100%
[42]		Japan	Sapporo		1981–2000	2090	46.7%
[51]		Finland	Vantaa		1980–2009	2100	82%
[47]		China	Jinan		2020	2080	80.3%
[50]		Lithuania	Kaunas	RCP8.5	2020	2080	1.8% to 2.1%

Table 2. Expected increase in building cooling demand during the end of the 21st century (2080–2100).

Study	Climate Zone	Country	City	Emission Scenario	Baseline Year	Projection Year	Cooling Demand Increase
[14]	A	United States	Miami	A2	1960	2080	50%
[22]		United States	Key West Florida		1961–1990		48%
[24]		Malaysia	Kuala Lumpur	-	2000		11.7%
[27]		Brazil	Belém	A2	2015		111%
[59]	B	UAE	Al-Ain	-	1961–1990	2100	23.5%
[32]		Spain	Granada	A2		2080	239%
			Salamanca				645%
[32]	C	United Kingdom	Aberdeen	A2	1961–1990	2080	23,600%
			Belfast				1100%
			London				3695%
		France	Bordeaux				434%
		Italy	Milan				468%
			Palermo				142%
			Pescara				313%
			Rome				272%
		France	Paris				853%
		Portugal	Porto				937%
[22]		United States	Tallahassee				80%
			Tampa				59%
			Daytona Beach				62%
[39]		Switzerland	Switzerland	-		2050–2100	223% to 1050%
[34]		China	Hong Kong	RCP4.5	1979–2003	2090	27.27%
				RCP8.5			54.25%
[42]		Japan	Tokyo	A2	1981–2000	2090	32.8%
			Naha				19.8%
[35]		Italy	Milan	RCP4.5	1982–1999	2081–2099	73.7%
				RCP8.5			174.3%
[22]		United States	Jacksonville	A2	1991–2005	2080	71%
			Orlando				61%
			Pensacola				74%
[43]		Taiwan	Taipei	A1B	1993–2014	2080	82%
[33]		United States	San Antonio	SSP126	2020	2100	24.5%
				SSP245			33.3%
				SSP370			57.8%
				SSP585			87%
			New York	SSP126			37.1%
				SSP245			47.5%
				SSP370			85.3%
				SSP585			121%
[41]		Australia	Canberra	A2	-	2080	19.6%
			Brisbane		-	2080	19% to 23.9%
[32]	D	Romania	Cluj-Napoca	A2	1961–1990	2080	871%
		Denmark	Copenhagen				2297%
		Sweden	Göteborg				30,945%
		Czech Republic	Prague				2318%
[14]		United States	Chicago		1960		80%
			Minneapolis				100%
[42]		Japan	Sapporo		1981–2000	2090	46.7%
[51]		Finland	Vantaa		1980–2009	2100	82%
[47]		China	Jinan		2020	2080	80.3%
[50]		Lithuania	Kaunas	RCP8.5	2020	2080	1.8% to 2.1%

Figure 4. Increase in cooling demand by the middle of the 21st century considering the same emission scenario (A2) and baseline period (1961–1990).

Figure 4. Increase in cooling demand by the middle of the 21st century considering the same emission scenario (A2) and baseline period (1961–1990).

5.2. Effect of Mitigation Strategies on Building Cooling Demand

Different strategies were proposed in the literature to mitigate the increase in building cooling demand in the studied climate zones. Table 3 outlines the effect of the mitigation strategies on reducing cooling demand in the present term. Table 4 and Table 5 show the influence of mitigation strategies on cooling demand in 2040–2080 and 2080–2100, respectively.

In the tropical climate zone (category A), installation of thermal insulation in buildings reduces the present cooling load from 3.5% to 12.1%. By comparison, a reduction of 3.8% to 6.1% in present cooling demand is achieved by implementing a solar shading strategy. Combining thermal insulation and solar shading leads to the highest reduction (19.4%) in cooling demand in the present climate [56]. The effectiveness of thermal insulation, WWR, and solar shading is expected to reduce in the middle of the 21st century due to climate change, by 4.7%, 0.9%, and 2.7%, respectively [28]. On the other hand, the effectiveness of efficient window strategies is expected to increase by 0.65% by the middle and end of the 21st century. Building cooling demand in the arid climate zone (category B) could be reduced by implementing different mitigation strategies. Applying a thermal insulation strategy was the best-proposed strategy in the present and 2050 climates. However, by 2080, a thermal mass strategy will have the largest reduction (18.6%) in building cooling demand [59]. The effectiveness of solar shading is expected to reduce by the end of the 21st century, as shown in Table 3, Table 4 and Table 5. On the other hand, the effectiveness of efficient window and WWR will double by the end of the 21st century [59].

In the temperate climate zone (category C), the highest reduction in cooling demand in the present climate was observed in Taipei, Taiwan [43], using thermal insulation and solar shading strategies. In contrast, natural ventilation increased the cooling demand in Gaza, Palestine, by 24.40%. In the middle of the 21st century, combining solar shading and natural ventilation was found to be the most effective strategy. Moreover, the effectiveness of thermal insulation is expected to decrease over time, as shown in the study [43]. Only two studies discussed mitigation strategies in the cold climate zone (category D). In Sapporo, combining thermal insulation, efficient window, solar shading, night ventilation, and modified indoor comfort temperature reduced cooling demand significantly at present and by the end of the 21st century [42], while the application of thermal insulation combined with efficient window strategy increased cooling demand in Quebec and Toronto by 19% to 22% in the middle of the 21st century [49].

Although this paper discusses mitigation strategies to decrease building cooling demand, applying such strategies might also affect other building demands. For example, applying thermal insulation and efficient window strategies could also reduce heating demands across different climate zones, which was proven in studies conducted in the arid [59], temperate [64,65], and cold [65] climate zones. On the other hand, solar shading could reduce cooling demand while increasing the demand for artificial lighting and heating [66,67]. Increasing heating demand is critical in countries located in temperate or cold climate zones. Previous studies have suggested that the position of solar shading should be controlled and adjusted according to the season, to reduce both cooling and heating demand [42,66,67]. Moreover, natural ventilation should be controlled based on indoor and outdoor temperature, to optimize heat absorption and avoid overcooling. Since WWR cannot be adjusted, it should be set to achieve optimum performance in terms of daylight and building energy efficiency throughout the year.

Table 3. Effect of mitigation strategies on present cooling demand.

Study	Climate Zone	Country	City	Strategies	Category	Cooling Demand Reduction
[56]	A	Madagascar	Antsiranana MahajungaToamasinaTaolagnaro	Thermal insulation	Thermal insulation	−9.6% to −12.1%
				Thermal insulation and PCM.
				Windows shading	Solar shading	−3.8%
				Thermal insulation and windows shading.	Thermal insulation and solar shading.	−19.4%
[28]		Ghana	Greater Accra Region	Thermal insulation	Thermal insulation	−11.9%
				WWR	WWR	−2.8%
				Window solar shading	Solar shading	−6.1%
[52]		United States	Miami	Roof and wall thermal resistance.	Thermal insulation	−3.5% to −5%
				Window visible transmittance	Efficient window	−2.73%
				Window solar transmittance		−2.73%
				Window thermal conductivity k−value		−1.97%
[60]	B	Qatar	Doha	Double glazed window	Efficient window	−5%
				Lighting efficiency	Efficient lighting	−10%
				Light color building shell	Light color building shell	−12%
				Wall insulation u−value (-)	Thermal insulation	−27%
				Indoor comfort temperature	Indoor comfort temperature	−14%
[58]		Iran	Tehran	Urban morphology	Urban morphology	−10%
[59]		UAE	Al-Ain	Thermal insulation	Thermal insulation	−19.3%
				Thermal mass	Thermal mass	−13.4%
				Solar shading devices	Solar shading	−3.7%
				Double glazing system	Efficient window	−5.4%
				WWR	WRR	−3.70%
[61]	C	Palestine	Gaza	Natural ventilation	Natural ventilation	24.40%
				Wall thermal insulation	Thermal insulation	−53.50%
				Window shading	Solar shading	−64.3%
[62]		China	Hong Kong	Window shading Glazing system Window openable area Window insulation Wall solar absorptance Wall insulation	Solar shading, efficient window, natural ventilation and thermal insulation.	−55.10%
[41]		Australia	Canberra	Wall insulation Shading deviceWindow type	Thermal insulation, solar shading and efficient window.	−56%
			Brisbane			−49%
[42]		Japan	Tokyo	Efficient glazing Thermal insulation Indoor comfort temperature Shading device Night cooling	Efficient window, thermal insulation and indoor comfort. temperature, solar shading and natural ventilation.	−63.4%
			Naha			−50.2%
[43]		Taiwan	Taipei	Thermal insulation	Thermal insulation	−54.5% to −70.9%
				Shading devices	Solar shading	−65.5%
[42]	D	Japan	Sapporo	Efficient glazing Thermal insulation Indoor comfort temperature Shading devices Night cooling	Efficient window, thermal insulation and indoor comfort. Temperature, solar shading and natural ventilation.	−79.9%

Table 3. Effect of mitigation strategies on present cooling demand.

Study	Climate Zone	Country	City	Strategies	Category	Cooling Demand Reduction
[56]	A	Madagascar	Antsiranana MahajungaToamasinaTaolagnaro	Thermal insulation	Thermal insulation	−9.6% to −12.1%
				Thermal insulation and PCM.
				Windows shading	Solar shading	−3.8%
				Thermal insulation and windows shading.	Thermal insulation and solar shading.	−19.4%
[28]		Ghana	Greater Accra Region	Thermal insulation	Thermal insulation	−11.9%
				WWR	WWR	−2.8%
				Window solar shading	Solar shading	−6.1%
[52]		United States	Miami	Roof and wall thermal resistance.	Thermal insulation	−3.5% to −5%
				Window visible transmittance	Efficient window	−2.73%
				Window solar transmittance		−2.73%
				Window thermal conductivity k−value		−1.97%
[60]	B	Qatar	Doha	Double glazed window	Efficient window	−5%
				Lighting efficiency	Efficient lighting	−10%
				Light color building shell	Light color building shell	−12%
				Wall insulation u−value (-)	Thermal insulation	−27%
				Indoor comfort temperature	Indoor comfort temperature	−14%
[58]		Iran	Tehran	Urban morphology	Urban morphology	−10%
[59]		UAE	Al-Ain	Thermal insulation	Thermal insulation	−19.3%
				Thermal mass	Thermal mass	−13.4%
				Solar shading devices	Solar shading	−3.7%
				Double glazing system	Efficient window	−5.4%
				WWR	WRR	−3.70%
[61]	C	Palestine	Gaza	Natural ventilation	Natural ventilation	24.40%
				Wall thermal insulation	Thermal insulation	−53.50%
				Window shading	Solar shading	−64.3%
[62]		China	Hong Kong	Window shading Glazing system Window openable area Window insulation Wall solar absorptance Wall insulation	Solar shading, efficient window, natural ventilation and thermal insulation.	−55.10%
[41]		Australia	Canberra	Wall insulation Shading deviceWindow type	Thermal insulation, solar shading and efficient window.	−56%
			Brisbane			−49%
[42]		Japan	Tokyo	Efficient glazing Thermal insulation Indoor comfort temperature Shading device Night cooling	Efficient window, thermal insulation and indoor comfort. temperature, solar shading and natural ventilation.	−63.4%
			Naha			−50.2%
[43]		Taiwan	Taipei	Thermal insulation	Thermal insulation	−54.5% to −70.9%
				Shading devices	Solar shading	−65.5%
[42]	D	Japan	Sapporo	Efficient glazing Thermal insulation Indoor comfort temperature Shading devices Night cooling	Efficient window, thermal insulation and indoor comfort. Temperature, solar shading and natural ventilation.	−79.9%

Table 4. Effect of mitigation strategies on building cooling demand during the middle of the 21st century (2040–2080).

Study	Climate Zone	Country	City	Strategies	Category	Cooling Demand Reduction
						Target Year	%
[52]	A	United States	Miami	Roof and wall thermal resistance	Thermal insulation	2050	−3.5 to −5%
				Window visible transmittance	Efficient window		−3.13% to−3.35%
				Window solartransmittance
				Window thermal conductivity
[28]		Ghana	Greater Accra Region	Thermal insulation	Thermal insulation		−7.2%
				WRR	WRR		−1.9%
				Window solar shading	Solar shading		−3.4%
[59]	B	UAE	Al−Ain	Thermal insulation	Thermal insulation	2050	−19.7%
				Thermal mass	Thermal mass		−12.6%
				Solar shading devices	Solar shading		−3.4%
				Double glazing system	Efficient window		−5.5%
				WRR	WRR		−3.9%
[35]	C	Italy	Milan	Envelope thermal insulation	Thermal insulation	2021–2040	−15.6% to −19.7%
[63]		Switzerland		Window shading	Solar shading	2050	−71%
				Night ventilation	Natural ventilation		−38%
				Window shading and night ventilation.	Solar shading and natural ventilation.		−84%
[43]		Taiwan	Taipei	Thermal insulation	Thermal insulation		−31.3 to −42.3%
				Shading devices	Solar shading		−37.5%
[49]	D	Canada	Quebec	Wall insulation andtriple glazing	Thermal insulation and efficient window	2056–2075	+19.5%
			Toronto				+22.2%

Table 4. Effect of mitigation strategies on building cooling demand during the middle of the 21st century (2040–2080).

Study	Climate Zone	Country	City	Strategies	Category	Cooling Demand Reduction
						Target Year	%
[52]	A	United States	Miami	Roof and wall thermal resistance	Thermal insulation	2050	−3.5 to −5%
				Window visible transmittance	Efficient window		−3.13% to−3.35%
				Window solartransmittance
				Window thermal conductivity
[28]		Ghana	Greater Accra Region	Thermal insulation	Thermal insulation		−7.2%
				WRR	WRR		−1.9%
				Window solar shading	Solar shading		−3.4%
[59]	B	UAE	Al−Ain	Thermal insulation	Thermal insulation	2050	−19.7%
				Thermal mass	Thermal mass		−12.6%
				Solar shading devices	Solar shading		−3.4%
				Double glazing system	Efficient window		−5.5%
				WRR	WRR		−3.9%
[35]	C	Italy	Milan	Envelope thermal insulation	Thermal insulation	2021–2040	−15.6% to −19.7%
[63]		Switzerland		Window shading	Solar shading	2050	−71%
				Night ventilation	Natural ventilation		−38%
				Window shading and night ventilation.	Solar shading and natural ventilation.		−84%
[43]		Taiwan	Taipei	Thermal insulation	Thermal insulation		−31.3 to −42.3%
				Shading devices	Solar shading		−37.5%
[49]	D	Canada	Quebec	Wall insulation andtriple glazing	Thermal insulation and efficient window	2056–2075	+19.5%
			Toronto				+22.2%

Table 5. Effect of mitigation strategies on building cooling demand during the end of the 21st century (2080–2100).

Study	Climate Zone	Country	City	Strategies	Category	Cooling Demand Reduction
						Target Year	%
[52]	A	United States	Miami	Roof and wall thermal resistance.	Thermal insulation	2080	−3.5% to −5%
				Window visible transmittance	Efficient window		−3.45% to −3.5%
				Window solar transmittance
				Window thermal conductivity k-value
[59]	B	UAE	Al-Ain	Thermal insulation	Thermal insulation	2100	−15.5%
				Thermal mass	Thermal mass		−18.6%
				Solar shading devices.	Solar shading		−2.9%
				Double glazing system	Efficient window		−10.5%
				WRR	WRR		−9%
[62]	C	China	Hong Kong	Window shading	Solar shading, efficient window, natural ventilation, and thermal insulation	2090	−56.7%
				glazing system
				Window openable area
				Window insulation
				Wall solar absorptance
				Wall insulation
[35]		Italy	Milan	Envelope thermal insulation	Thermal insulation	2081–2099	−24.3% to −63.5%
[41]		Australia	Canberra	Wall insulation Shading device Window type	Thermal insulation, solar shading and efficient window.	2080	−54%
			Brisbane				−46.7%
[42]		Japan	Tokyo	Efficient glazing Thermal insulation Indoor comfort temperature Shading device Night cooling	Efficient window, thermal insulation, indoor comfort temperature, solar shading and natural ventilation.	2090	−57.4%
			Naha				−43.5%
[43]		Taiwan	Taipei	Thermal insulation	Thermal insulation	2080	−22.8% to −33.2%
				Shading devices	Solar shading		−27.7%
[42]	D	Japan	Sapporo	Efficient glazing Thermal insulation Indoor comfort temperature Shading devices Night cooling	Efficient window, thermal insulation, indoor comfort temperature, solar shading and natural ventilation.	2090	−71.97%

Table 5. Effect of mitigation strategies on building cooling demand during the end of the 21st century (2080–2100).

Study	Climate Zone	Country	City	Strategies	Category	Cooling Demand Reduction
						Target Year	%
[52]	A	United States	Miami	Roof and wall thermal resistance.	Thermal insulation	2080	−3.5% to −5%
				Window visible transmittance	Efficient window		−3.45% to −3.5%
				Window solar transmittance
				Window thermal conductivity k-value
[59]	B	UAE	Al-Ain	Thermal insulation	Thermal insulation	2100	−15.5%
				Thermal mass	Thermal mass		−18.6%
				Solar shading devices.	Solar shading		−2.9%
				Double glazing system	Efficient window		−10.5%
				WRR	WRR		−9%
[62]	C	China	Hong Kong	Window shading	Solar shading, efficient window, natural ventilation, and thermal insulation	2090	−56.7%
				glazing system
				Window openable area
				Window insulation
				Wall solar absorptance
				Wall insulation
[35]		Italy	Milan	Envelope thermal insulation	Thermal insulation	2081–2099	−24.3% to −63.5%
[41]		Australia	Canberra	Wall insulation Shading device Window type	Thermal insulation, solar shading and efficient window.	2080	−54%
			Brisbane				−46.7%
[42]		Japan	Tokyo	Efficient glazing Thermal insulation Indoor comfort temperature Shading device Night cooling	Efficient window, thermal insulation, indoor comfort temperature, solar shading and natural ventilation.	2090	−57.4%
			Naha				−43.5%
[43]		Taiwan	Taipei	Thermal insulation	Thermal insulation	2080	−22.8% to −33.2%
				Shading devices	Solar shading		−27.7%
[42]	D	Japan	Sapporo	Efficient glazing Thermal insulation Indoor comfort temperature Shading devices Night cooling	Efficient window, thermal insulation, indoor comfort temperature, solar shading and natural ventilation.	2090	−71.97%

6. Conclusions

Climate change has several negative impacts on our planet. The built environment sectors are among the victims of climate change; however, among these sectors, building cooling is significantly affected. The future cooling requirements of buildings vary from one climatic zone to another. This paper reviewed how climate change impacts building cooling requirements in varying climate zones, and the proposed strategies to mitigate this impact. Building cooling demand is expected to increase in all climate zones. Under future climate conditions, temperate and cold climate zones will face a significant increase (%) in building cooling demand compared with tropical and arid zones. This significant increase is due to the absent and low cooling demand in the baseline climate, where such countries are expected to face a shift in days with comfortable indoor temperatures, to warm days that require cooling. On the other hand, a slight increase (%) in building cooling requirements in tropical and arid climates could severely impact existing cooling systems since they are already overloaded under the current climate. Further research should be conducted to investigate the capability of existing cooling systems in hot countries to handle the expected increase in cooling demand under climate change.

Thermal insulation was found to be the most effective strategy to mitigate the surge in cooling demand in present and future climate conditions in the tropical climate zone (category A). In the arid climate zone (category B), thermal insulation had the highest reduction in cooling demand in the present time and middle of the 21st century; however, the application of thermal mass was more effective at the latter end of the 21st century. The best two strategies in the temperate climate zone (category C) were solar shading and thermal insulation, in the present climate, while at middle of the 21st century, a combination of solar shading and natural ventilation was the most effective technique. Few studies have discussed mitigation strategies in the cold climate zone (category D), and more effort should be invested to investigate how to reduce future cooling demand in this zone.